pick your negative size (format) first
pick your negative size (format) first
I did exactly what you're pondering. Medium format film equipment is going for a song lately, as all the pros go over to high-end DSLRs or digital MF backs.
I would suggest that you pick your negative format (ie, size) first. Here's my 30-second discussion of the various sizes:
6x4.5 cm is the entry level Medium Format negative. It makes good use of film (16 frames on a 120 roll, so 32 on a 220 roll), and it's well suited to most print sizes (5x7, 8x10, etc). You're still way ahead of 35mm in terms of negative size, so grain is relatively less important in big enlargements. You can print four images across the 8 inch side of your 8x10 contact sheet. A "normal" lens in this negative size is the 75mm.
6x6 cm is 'the standard' in a domain which eschews standards. An advantage of 6x6 is that you never have to rotate the camera 90 degrees to switch from landscape to portrait orientation. However, all of the common print sizes are rectangular (4x6, 5x7, 8x10, etc), so you're throwing away some large part of the image when you make prints to those rectangular frames. Sometimes you'll be glad to have the option to crop 'portrait' or 'landscape' in the same frame, but most of my images are pretty obviously one or the other. You'll get 12 frames on a 120 roll with 6x6, and strips of three frames will fit on the 8 inch side of your contact sheet. A "normal" lens in 6x6 is around 80mm.
6x7 is a nice large image, close enough to 6x6 that you can keep the camera horizontal for quick grabs and not lose much compared to rotationg 90 degrees. This size doesn't lend itself well to contact prints sideways on 8x10 IMO; you might wind up wasting some paper. But since the 6x7 negative is proportioned almost the same as 8x10, it's just about ideal for enlargement to that size print without having to crop off much of the image. (for sake of comparison, 6x7 needs to be enlarged 3.2 times to make an 8x10 print, and 6x6 needs to be enlarged 4 times for the same print. That's a big difference, which comes from the more suitable aspect ratio)
6x9 is marvelously large, the contact prints are almost postcards. You'll get around eight frames on a roll of 120 film. Contact prints will be two across, and you won't need a loupe to proof them.
😛 A "normal" lens in 6x9 is around 90mm.
If you're interested in how the focal lengths stack up, check out
http://www.photo.net/equipment/medium-format/focal-length-conversion or google the subject of 35mm equivalent focal length.
As for me, 6x4.5 has been great. I got a Bronica ETRSi, and followed it with a Bronica RF645 rangefinder.
The ETRSi is a real workhorse camera, very easy to use, cheap as dirt on the Bay, with good glass available (get the PE lenses, the coatings are better than the earlier MC or E lenses) and lots of accessories. The metering prism finders (AE-II or AE-III) integrate well with the camera body, allowing aperture-priority auto exposure or manual metering. There are good zoom lenses available, yes, that's right, zoom lenses in medium format! I have the PE 100-220, which is fantastic for product shots in the studio, it's darn near a macro lens. There's a flash adapter which allows TTL flash metering, and Metz Mecablitz flashes are similarly bargain priced these days. Prices are unbelievably low; I got the 100-220 zoom lens from KEH for $300, and the 50-75-150 primes regularly go for less than $200 on the Bay.
Basically, I've been very happy with the ETRSi camera. If you like the camera but want square format (6x6 cm), then the SQ series is equivalent. The equivalent in 6x7 cm is the Bronica GS series, and they didn't make one in 6x9.
Of course, the Bronica RF645 rangefinder is a dream to shoot with. It wasn't quite such a bargain as the ETRSi, but it handles leica big leica, and the image is 3.7 times bigger than 35mm. Bliss!
The quality of most medium format systems is excellent. Most cameras have leaf shutters, which allow flash sync at all speeds. The optics are generally very good, though not fast by 35mm standards. (f/2.8 is considered 'fast' in medium format lenses)
Good luck, let us know what you decide!
Mark
ps, you won't be sneaking up on anyone with a medium format SLR. These are big cameras, noisy when the mirror cycles, etc. For studio work, that's no problem, but for street photography, the medium format rangefinders (Mamiya 6/7, Bronica RF, et al) are unbeatable.